The limestone component is calcium carbonate. Lime includes quicklime and hydrated lime. The main ingredient of quicklime is CaO, which is generally lumpy and pure white. When it contains impurities, it is mainly dispelling particles or light yellow. The slaked lime is adjusted into lime slurry, lime paste, lime mortar, etc., cement coating materials and brick preparations. Also called in some places: calcite, lime, white lime, limestone, white marble.
The main component of limestone
Limestone is an aggregate of minerals. The chemical formula of limestone is CaCO3. The main mineral component is calcite, followed by dolomite, magnesite and other carbonate minerals, in addition to chalcedony, clay, pyrite, and marcasite , Water goethite, sea green stone, organic carbon, asphalt, gypsum, anhydrite and phosphate and other minerals. The chemical composition of pure limestone is close to the theoretical composition of CaCO3, with CaO accounting for 56.04% and CO2 accounting for 43.97%.
What is the use of limestone?
Calcium carbonate is the main component of limestone, and limestone is the main raw material for glass production. Lime and limestone are widely used as building materials and are also important raw materials for many industries. Calcium carbonate can be directly processed into stone and burned into quicklime. After being processed, limestone can be used in the following industries:
- Cement industry
Limestone is the main raw material of cement, accounting for 70 to 90% of the raw material composition. The ingredients are clay raw materials, siliceous raw materials, and iron-aluminum raw materials.
- Plastic industry
Calcium carbonate is the most widely used and most used inorganic mineral powder material. As a commonly used powder material for plastics, calcium carbonate has many advantages that other powder materials do not have, such as high whiteness, easy surface organic treatment, and processing The equipment and molds have light abrasion, good molding processing fluidity, etc., combined with abundant resources and low prices, it has become the first choice for inorganic mineral powder materials in the plastics processing industry.
- Rubber industry
For rubber, calcium carbonate is the third largest reinforcing filler after carbon black and white carbon black. It has the characteristics of low toxicity, low price, and good reinforcing effect.
- Coating industry
Heavy calcium carbonate is the world’s first filler in the coating industry. It is not only cheap, but also can greatly reduce the production cost of the coating. As one of the functional fillers, it can affect many properties of the coating, such as changing the mechanical strength of the coating film. , Improve the water resistance and chalking resistance of the coating film. Because it is a high-quality and inexpensive functional filler, calcium carbonate has always been one of the most important basic substances in the composition of coatings in civil and industrial coatings.
- Paper industry
Calcium carbonate is one of the main inorganic chemical raw materials in the paper industry. The calcium carbonate used as paper filler and paper coating pigment can be classified into two categories: one is natural calcium carbonate (GL) made from ground limestone, and the other is chemical A synthetic product made by precipitation-precipitated calcium carbonate (PCC). The purpose of adding fillers in papermaking is to increase the opacity and brightness of the paper, improve the smoothness and uniformity of the paper, increase the softness of the paper, and reduce the moisture absorption and deformation of the paper. For printing paper, the ink absorption and printability of the paper are enhanced after filling. Adding fillers to a larger extent is also beneficial to reduce paper costs.
- Food industry
Pure mineral calcium carbonate, using various processes to remove harmful substances in minerals, such as heavy metal ions, etc., is prepared into relatively pure calcium carbonate, which is used as an additive to various foods. Calcium carbonate can be used as additives, supplements, curing agents, anti-caking agents, yeast sugar additives, calcium supplements and modifiers in foods. Some foods are darker or darker in color, resulting in unsatisfactory visual effects. When required, calcium carbonate is added to whiten, increase the visual effect, and meet the needs of consumers; calcium carbonate can also be used as a leavening agent and starter in some foods to reduce the fermentation time.
- Pharmaceutical industry
In the prevention and treatment of osteoporosis and other related diseases, calcium carbonate is the most widely used because of its high calcium content, low price, no side effects, and the best effect-price ratio. Although there are more than a dozen calcium salts as calcium supplements, calcium carbonate preparations are the best calcium supplements that are most widely used, contain the highest calcium content, have good effects, and are low in price.
Limestone production and processing process
1.Sand and gravel
For building aggregates: generally processed to 1-2cm.
Production of sand: vibrating feeder–limestone jaw crusher–sand making machine–belt conveyor–sand washing machine for sand and gravel aggregates.
Molding sand: The particle size of the casting sand produced by limestone is 28～75 mesh. This type of molding sand has better performance than quartz sand, has good collapsibility, is easy to clean up, improves the surface quality of castings, and increases the surface finish of castings.
2. Production of quicklime: (limestone -> calcination (rotary kiln) -> calcium oxide (calcined generally in block form))
The process flow of producing lime in rotary kiln:
⑴Limestone→vibrating feeder→belt conveyor, from the raw material warehouse to the screening equipment, the limestone of appropriate size enters the preheater, the kiln tail is preheated at 1000℃, and 20%-25% of the limestone is decomposed→advancing the rotation kiln.
⑵Further calcined in the rotary kiln, completely decomposed at 1300℃.
⑶ When entering the cooler, its temperature is 1100℃, and the lime is cooled to 70-100℃ by the blower at the bottom of the cooler. Then there is a vibrating feeder in the lower part of the cooler to discharge it to the conveyor, and then send it to the finished product warehouse through conveying, screening, and lifting equipment, which is the final active lime product.
Uses: water treatment, desulfurization, building materials, medicine.
3. Limestone powder is used for chemical fillers.
Papermaking: 200 mesh or more
Rubber, plastic: above 400 mesh
Coating, coating: 600 mesh or more
Ink: above 1500 mesh
The finished products of milling powder mainly include: light calcium, heavy calcium, calcium hydroxide, ash calcium, double fly powder.
Limestone is processed into gray calcium powder to make putty powder: about 400 mesh
200 mesh for desulfurization
Ordinary putty powder 280 mesh is enough
The main process of limestone grinding requires four stages
Customers can purchase related equipment according to their needs. The first stage: coarse crushing, the second stage: medium and fine crushing, the third stage: grinding, the fourth stage: packaging. The specific processing flow is as follows:
- The first stage: coarse crushing
Large pieces of limestone materials are uniformly fed by a vibrating feeder through the silo, and then transported to the jaw crusher for coarse crushing. After the coarsely crushed materials are screened by the vibrating screen, they are transported to the impact crusher by a belt conveyor.
- The second stage: medium and fine crushing
After the coarse material transported to the impact crusher is crushed by the impact crusher, the circular vibrating screen is used to screen the crushed materials through the impact crusher, and the larger particle materials are returned to the impact crusher and crushed again; if finer products or shaping are required, The crushed materials are sent to the sand making machine for further crushing and shaping.
- The third stage: grinding
The crushed small pieces of limestone are sent to the silo by the elevator, and then sent to the grinding machine chamber of the mill evenly and quantitatively by the vibrating feeder for grinding.
- The fourth stage: packaging
Pack and store finished materials.